Technology Applications Center
Powder Paint/Powder Coating
A paint that is 100% dry solids, in a fine powder, requiring thermal energy to flow into a semi-liquid state, followed by additional heating to complete a cross-linking process to form a hard, durable, protective solid coating.
Today's Electric Technologies: Used to reduce the curing cycle time for powder paints
When the question is asked as to how long it takes for powder paint to reach its full cure state, most will refer to the rate of cure information provided by the powder coat supplier. For example, the average curing time ranges from 10 to 20 minutes after the part being painted reaches the recommended temperature. Today more coaters are finding they are able to shorten this time by using booster infrared and hybrid combination curing ovens, while still passing quality inspection tests. Working with your paint supplier you can take advantage of accelerated curing offered by infrared, induction, and ultraviolet.
Curing powder paint of heavy mass using infrared.
The Infrared (IR) Advantage
Infrared or radiant heating is ideally suited for curing powder paints. That's because infrared energy is quickly absorbed by the powder itself, gaining heat very fast to the temperature required to flow or melt the powder. In most cases, this can be process designed to happen in less than a minute. With the flow of the powder completed and the temperature of the part already at about 220° F, the next heating step is to continue to accelerate the temperature of the part to the target temperature for curing. If the powder cures at 350° F, that temperature can be reached just as quickly as the flow temperature was reached. To complete the cross-linking, a little more time is added to hold the part at temperature, usually a few more minutes.
Speed of Induction Curing
If the application parameters for using induction as a curing method are met, the curing times can be from a few seconds to just a few minutes using standard formulated powders. While there are a limited number of manufactured products that can take advantage of induction curing, generally parts having a consistent shape and thickness, induction curing should still be evaluated for possible application. An example of a product line very suitable for using induction is the curing of paint on metal coil sheet and coatings on tubing and pipe. In the mid-1990s, the Southern Company Technology
Applications Center had a supporting role in evaluating a high speed metal handle production line for fast technology curing opportunities. Induction fit the application perfectly with a curing time of three (3) seconds achieved on a production line speed of 600 ft/min. This three (3) second cure time was achieved using standard formulated powders available at the time.
Curing powder paint on metal using induction.
Running Q-panel test using ultraviolet.
Ultraviolet (UV), the new generation of powder paints
The use of ultraviolet technology for curing UV formulated powder paints has application opportunities with products that are considered heat sensitive substrates and can not tolerate the elevated temperatures required to cure traditional thermo-set powders. These substrates include wood, MDF, plastics and products with heat sensitive parts such as bushings, wires or the like. UV curable powders still requires, a component of heat to flow UV powder just as with thermo-set powder. The difference in the two types of powders comes after the flow when the powder is exposed to UV energy with the curing process being accomplished is seconds. An application example can be found at a leading electric motor manufacture that is powder coating fully assembled motors. By using UV curable powders, this manufacturer can offer a high quality finish with the durability of the thermo-set powders without the introduction of high temperatures to the internal wiring of the motor.
While the number of applications for UV curable powders is considered small compared to standard powder applications, suppliers of UV powders are investing in research and development to grow the application and use of UV curable powders. Southern Company's Technology Applications Centers can demonstrate UV curable powders. We encourage you to bring in your part to the TAC for a UV powder paint curing evaluation. Call your account representative to set up an appointment or Contact Us.